TurtleSerializer.hs: fixed problem with base and prefix not having brackets before and after, and minor cleanup of compiler warnings.
TurtleSerializer.hs: fixed problem with base and prefix not having brackets before and after, and minor cleanup of compiler warnings.

darcs-hash:20071121084130-db1bb-18c7d4183522a665f75225cc1d654268a942eff2

jutaro/rdf4h,cordawyn/rdf4h,ddssff/rdf4h,LeifW/rdf4h